A gas turbine engine combustor is a pressure vessel provided with pressurized airflow from a compressor disposed upstream thereof. The compressed airflow is channeled to carburetors disposed in a dome end of the combustor wherein it is mixed with fuel for generating a fuel/air mixture for combustion in the combustor. A portion of the compressed airflow is also provided around the liner walls through which it is conventionally channeled for providing cooling-and dilution air into the combustor. The pressure of the compressed airflow external of the combustor is greater than the pressure of the combustion gases inside the combustor which results in external gas pressure loads being applied to the combustor liners which must be suitably accommodated for providing acceptable buckling resistance margin in the combustor.
Combustor liners are typically made from conventional high temperature sheet metal or relatively thin castings and therefore inherently have relatively low buckling resistance capability. Accordingly, conventional stiffening rings are typically provided at least on the combustor outer liner which is subject to the buckling gas pressure loads for providing acceptable buckling resistance margin. The stiffening rings may comprise a plurality of axially spaced circumferentially extending rings for providing increased stiffness, or circumferentially spaced, axially extending stiffening flanges. Such stiffening rings may be used in addition to relatively flexible conventional cooling rings or nuggets which provide film cooling air along the inner surface of the liners for providing acceptable cooling thereof. In some conventional embodiments, the cooling nuggets may be relatively large for providing by themselves adequate stiffness for accommodating gas pressure buckling loads applied to the outer liner.
Conventional cooling nuggets are typically in the form of annular rings extending around the circumference of the combustor and form an integral part of the liners. The nuggets have a generally u-shaped longitudinal profile for defining an annular plenum for receiving a portion of the compressed airflow from outside the combustion liner. The nuggets also include an aft facing annular slot for directing the cooling air as an annular film along the inner surface of downstream portions of the liner for providing effective film cooling thereof.
It is desirable to eliminate such stiffening rings for reducing complexity, weight, and cost of the combustor. It is also desirable to eliminate the cooling rings for reducing complexity, weight, and most significantly, the amount of cooling air required for cooling the combustor liners. The efficiency of the combustor, and therefore of the gas turbine engine, can be increased if less of the compressed airflow is used for cooling the combustor and is instead used for mixing with fuel and undergoing combustion. However, without the use of such stiffening rings and cooling rings, the stiffness of the combustor liners would be substantially reduced thus leading to undesirable buckling thereof unless other means for accommodating the gas pressure buckling loads are used.